The invention concerns a casting roll for a twin-roll casting machine, especially for casting steel strip, with a cylinder sleeve, which rotates on a stationary axle.
Casting machines of this type work in such a way that, during the operation, the molten metal present in the mold space flows through the casting gap between the counterrotating casting rolls and is shaped into a metal strip.
Due to the high thermal load, the casting sleeves experience convex deformation, which results in a concave profile of the cast strip. This can result in diminished strip quality, especially since the cooling of the strip also causes transverse shrinkage of the strip. For this reason, the casting rolls are concavely shaped in the cold state, so that thermal expansion of the casting rolls produces a parallel or slightly convex shape of the strip, which allows noncritical transverse contraction during cooling of the strip and guarantees the accuracy to gage of the strip.
However, a disadvantage of casting rolls of this type is that, due to their concave shape, they can be used only for a certain influx of molten metal and thus heat input into the casting rolls. If the production parameters and thus the amount of molten metal flowing into the mold are changed, a different heat input and thus different thermal deformation of the casting rolls are obtained, which can result in the cast strip no longer being accurate to gage. The result of all this is that the casting rolls need to have different geometries for different production parameters.
Another disadvantage of concave casting rolls arises during the starting up of the casting machines without a dummy bar. Since in this case the casting gap cannot be completely closed when the casting rolls are run together, liquid steel then leaks out at the bottom, which makes a controlled start-up more difficult.